1. Field of the Invention
The present invention is related to electrical connector receptacles commonly known as modular jacks and, more particularly, is directed towards a double-ended modular jack or coupler for use as an interconnect device between two multi-conductor cables, each terminated by a modular plug.
2. Description of Related Art
The desirability of providing a double-ended connector receptacle or modular jack for end-to-end connection of modular plugs has been recognized in the following U.S. Pat. Nos. 4,153,327; 4,268,109; 4,273,402; 4,367,908; and 4,379,609. The couplers taught in these patents are characterized by the provision of a dielectric housing and a pair of cavities opening into each end thereof. Each cavity is particularly designed and sized to receive a mating modular plug of the type described, for example, in U.S. Pat. No. 3,954,320 to Hardesty. Modular plugs and jacks have gained wide acceptance in the communications industry, as well as for use with general electrical and electronic equipment as interconnect devices.
An improved double-ended modular jack is described in U.S. Pat. No. 4,460,234, assigned to the same assignee as the present invention. In the '234 patent, a plurality of side-by-side conductors are employed which have a greatly reduced length compared with the conductors of the previously known couplers. This results in substantial cost savings both with respect to the overall reduced length of the conductors themselves, as well as with respect to the reduced amount of gold-plating thereof which is provided to increase conductivity and reliability.
While an improvement over prior known designs, the coupler described in the '234 patent nevertheless has a few drawbacks of its own. For one thing (and this is a problem which is common to all previously known modular jacks), the design of the spring contact portions of the conductors provides only a small area of electrical contact with the contact terminals of the male modular plug. Prior art modular jacks utilize a linear (or slightly curved) diagonally extending spring contact portion that makes contact with only the crown, or radiused end, of the contact terminal of the modular plug. This results in essentially a single point of electrical contact between the two components of approximately 0.0008 inch in diameter. Several problems arise from this configuration. For one thing, when the conductors are carrying high frequency signals (e.g., 20-40 MHz.), some information can be lost due to the small area of contact (i.e., signal transfer area) between the plug and jack conductors.
Another problem with such spring contact configurations is that they do not provide a uniform contact resistance as the plug is inserted and withdrawn into and from the jack. This results from the fact that such spring contact portions have a longitudinal force vector which increases and thus creates more resistance to longitudinal movement of the plug as the plug is inserted more deeply into the plug-receiving opening of the jack. Conversely, the contact resistance lessens as the plug is withdrawn from the cavity.
The single point of contact between the jack's spring contact portion and the plug's contact terminal is also disadvantageous when the connectors are utilized in an environment which is subject to vibration. In such a case, electrical continuity may be intermittently and undesirably broken.
A further disadvantge of the prior art spring contacts is that they may be easily overstressed if the wrong size plug is accidentally inserted into the jack. Such overstress degrades contact reliability and essentially ruins the jack for subsequent use.
In addition to the foregoing, the prior art couplers make no provision for selectively but permanently commoning two or more conductors in order to minimize the number of contact positions and wires required on one end of the coupler to carry a particular signal (such as tip or ring) that may come in on the other end of the coupler in more than one position. While the '234 patent does teach a shorting bar arrangement (see FIGS. 7 and 8 and column 7 from line 34), the shorting bar only comes into play when the modular plug is withdrawn from the coupler; it is ineffective when the modular plugs are mated in the double-ended jack. I have discovered that it would be very desirable to provide a double-ended modular jack with the capability of selectively and permanently commoning two or more conductors regardless of whether the modular plugs are in place in the jack.
The present invention is provided to overcome the above-noted deficiencies and as an improvement over known modular jack couplers.